In many industrial processes, suspensions of solids in liquids are obtained which need further treatment with gases. Many of these suspensious, however, have a tendency to coagulate or deposit sediments. The gassing of suspensions is particularly effective when the gaseous phase is introduced into the liquid container from below. Problems occur, however, when the gas inlet is used discontinously. These consist in that the liquid medium in the inlet nozzle can be forced back to the shut-off valve. If the suspensions in this case are, for example, suspensions that are sensitive to coagulation or have a tendency to deposit sediment, then incrustations or deposits in the inlet nozzle must be reckoned with. As a result of these, the operational reliability of the gassing equipment is impaired. To some extent, relief can be afforded by so-called disc valves, but a fine distribution of the gas stream introduced is not possible with these, and the risk of deposits of condensate, for example, upon the introduction of water vapor, cannot be adequately suppressed.